The present invention relates to a distributor for spark-ignited internal combustion engines, and more particularly to the electrode construction and material, and the method of their manufacture, to provide high-resistance distributor electrode elements to improve the radio interference noise suppression characteristics of the distributor.
The customary distributor construction and system, which is not basically changed, provides for a cylindrical structure in which a plurality of fixed electrodes are located on the circumference of an imaginary cylindrical surface. The electrodes are connected over high-tension spark plug wires to spark plugs. A distributor rotor is located internally of the distributor which has a central distributor contact, rubbing against a carbon pin or carbon brush. The carbon pin or central contact is connected to the secondary of a spark plug coil, and the tip of the rotor is formed with a terminal electrode which passes closely by the fixed electrodes to form a conductive spark connection therewith if current through the ignition coil is suddenly interrupted while the distributor rotor tip is opposite one of the fixed electrodes as it rotates within the distributor.
The spark breakdown within the distributor causes radio interference and other noise in electronic apparatus which may be installed close to the internal combustion engine, typically in an automotive vehicle to which the present invention is especially adapted. It has previously been proposed--see German Pat. No. 1,123,866--to construct a distributor rotor electrode of electrically highly conductive material and placing a noise suppression resistor mechanically as well electrically ahead of the distributor rotor electrode. Suppression of electrical interference radiation, caused by the spark breakdown between the rotor electrode and the respective fixed electrode which is opposite to the rotor electrode at any given instant, is the more effective, the closer the suppression resistor is to the spark gap itself. Placing a separate resistor close to the distributor electrode is difficult and limits to the closeness of location thereof to the spark gap itself arise due to mechanical difficulties. A relatively high arc-over current still results, requiring a high resistance and high current carrying suppression resistor which, in turn, requires a sturdy mechanical construction. Otherwise, the resistor may be overloaded or the noise radiation cannot be effectively suppressed.